This invention relates to a method of transmitting data via a data transmission unit between data processing units of a data processing system. The data processing system is, e.g., a stored program control to automate an industrial installation, in particular a machine, a manufacturing plant or a power plant. The invention also relates to a data processing system.
Data processing systems are used in a variety of ways in industrial automation processes. In complex industrial installations, a plurality of data processing units are combined into complex computer networks and data networks via a data transmission system that has at least one data processing unit. Usually, so-called operator stations or operation and observation units are provided for operating and/or observing the data processing units that control the installation. Each data processing unit has data processing programs for controlling and/or regulating the industrial installation. The data processing program usually runs in the data processing units of the industrial installation and controls, among other things, the exchange of data between the central control unit and components of the industrial installation via the data transmission unit. Therein, the data processing units are, e.g., a central control unit or decentralized on-site controllers. On the one hand, the data processing program transmits switching commands or control values to components, such as actuators. On the other hand, the data processing program reads measured data or characteristic process parameters and/or operating parameters from the components, such as sensors. Depending on the type and design of the industrial installation, a data processing unit may also gain access to the data processing program of another data processing unit.
Usually, when data are exchanged via the data transmission system that has at least one data transmission unit, so-called control signals, address signals and data signals are transmitted between communication partners in accordance with a protocol, i.e., in accordance with rules for time and signal level specifications. Therein, the data transmission system is, e.g., a bus system, and the communication partners are, e.g., data processing units. As the complexity of data processing systems steadily increases due to a steady increase in the number of functions, sensors and actuators, there is also an increase in the networking and, thus, in the exchange of data or information, such as sensor data and control commands. Therein, the communication or data transmission system must have a high level of interference immunity, in particular for security-relevant functions, and must permit especially rapid data transmission.
To achieve a high interference immunity in a communication relationship, in particular when a central controller communicates with process-oriented, decentralized peripheral modules, the data is sent to the peripheral modules via a low-pass filter. This results in a limited bandwidth in the communication relationship, thus limiting the data exchange with regard to the speed and volume of data. Therefore, usually, an increasingly faster data connection and/or data transmission is necessary to meet higher demands regarding data transmission between the central controller and the peripheral modules, for example, or to meet higher demands regarding a connection to the Ethernet, Internet or a bulk memory. To this end, additional bus systems are usually employed in the automation system or in the data processing system. However, expanding the data processing system by adding additional bus systems is especially complicated, and particularly complex and maintenance-intensive with respect to coordinating the data exchange.